dextromethorphan---quinidine-combination and Mood-Disorders

Fixed-dose dextromethorphan/quinidine capsules (Nuedexta(®)) utilize quinidine to inhibit the metabolism of dextromethorphan, enabling high plasma dextromethorphan concentrations to be reached without using a larger dose of the drug. The drug combination is the first treatment to be approved for pseudobulbar affect (PBA), a condition of contextually inappropriate/exaggerated emotional expression that often occurs in adults with neurological damage conditions, such as amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), stroke, traumatic brain injury, Alzheimer's disease or Parkinson's disease. Dextromethorphan/quinidine at the recommended dosages of 20/10 or 30/10 mg twice daily reduced the rate of PBA episodes and improved PBA severity in a 12-week, double-blind, placebo-controlled trial in adults with ALS or MS (STAR), with further improvements in the severity of the condition observed in a 12-week open-label extension phase. Dextromethorphan/quinidine 20/10 mg twice daily also improved PBA secondary to dementia in a cohort of a 12-week noncomparative trial (PRISM II). The drug combination was generally well tolerated in these studies, with no particular safety or tolerability concerns. Although longer-term efficacy and tolerability data for dextromethorphan/quinidine 20/10 or 30/10 mg twice daily would be beneficial, current evidence indicates that it is a useful option in the treatment of adults with PBA.

Topics: Adult; Dextromethorphan; Drug Combinations; Humans; Mood Disorders; Nervous System Diseases; Quinidine

Pseudobulbar affect is characterized by uncontrollable, inappropriate laughing and/or crying that is either unrelated or out of proportion to the emotions felt by the patient and occurs in patients with neurological disorders, such as amyotrophic lateral sclerosis (ALS), multiple sclerosis or traumatic brain injury. Dextromethorphan/quinidine is indicated in the US for the treatment of pseudobulbar affect. Dextromethorphan, when its metabolism is inhibited by the coadministration of quinidine, has been shown to have a positive effect on the symptoms of pseudobulbar affect. Dextromethorphan/quinidine 20 mg/10 mg twice daily was associated with a significantly greater decrease in the rate of pseudobulbar affect episodes per day (primary endpoint) than placebo in the 12-week, randomized, double-blind, placebo-controlled, multicentre STAR trial (Safety, Tolerability, And efficacy Results trial of AVP-923 in PBA [pseudobulbar affect]) involving patients with pseudobulbar affect and ALS or multiple sclerosis. Moreover, the mean change from baseline in Center for Neurologic Study-Lability Scale score at 12 weeks was significantly greater among recipients of dextromethorphan/quinidine 20 mg/10 mg twice daily than those receiving placebo. Dextromethorphan/quinidine 20 mg/10 mg twice daily was generally well tolerated. The drug has been shown to cause dosage-dependent corrected QT interval (QTc) prolongation; however, in the STAR trial, dextromethorphan/quinidine 20 mg/10 mg twice daily appeared to be well tolerated with regard to QTc prolongation.

Topics: Amyotrophic Lateral Sclerosis; Crying; Dextromethorphan; Drug Combinations; Emotions; Female; Humans; Laughter; Male; Mood Disorders; Multiple Sclerosis; Quinidine

Arising in settings of CNS insult, pseudobulbar affect (PBA) consists of uncontrollable episodes of crying or laughter incongruent to the patient's mood. The syndrome has been described by a plethora of names, including pathological laughing and crying, emotional lability, emotionalism and emotional incontinence, which hampers efforts to survey published assessments of pharmacological intervention. Still, until quite recently, all treatment has unavoidably been off-label, chiefly involving antidepressants. Using PBA and other syndrome names as search terms, a PubMed search for English-language case reports and therapeutic trials involving at least five patients identified 22 such publications from 1980 through to 2010. Among the seven randomized, double-blind, antidepressant studies with placebo control, two trials assessed 106 and 123 subjects, respectively. However, the other five assessed only 12-28 subjects, and only one of these seven trials (with 28 subjects) measured change in syndrome severity using a validated scale. The three randomized, double-blind studies of dextromethorphan plus quinidine assessed 129, 150 and 326 subjects. Among these studies, two were placebo-controlled and all three used a validated severity scale. Across all placebo-controlled trials, response to active treatment - either an antidepressant or dextromethorphan/quinidine - has in general been significantly greater than response to placebo, but placebo response has sometimes been substantial, suggesting caution in interpreting uncontrolled findings. In October 2010, dextromethorphan/quinidine received approval from the US FDA as first-in-class PBA pharmacotherapy. Advocates of a continuing role for antidepressants, notably selective serotonin reuptake inhibitors, can point to numerous positive case reports and trials, the potential benefit of attempting to treat PBA and concomitant depression without using multiple drugs, and the ever-present need to tailor treatment to the individual patient.

Topics: Antidepressive Agents; Crying; Dextromethorphan; Drug Combinations; Humans; Laughter; Mood Disorders; Off-Label Use; Quinidine

AVANIR Pharmaceuticals Inc, under license from Irisys Research & Development, is developing AVP-923 (Zenvia, Neurodex) for the treatment of pseudobulbar affect (PBA; in collaboration with Medison Pharma Ltd) and neuropathic pain associated with diabetic peripheral neuropathy. PBA, the main indication of AVP-923, is a neurological disorder characterized by uncontrollable and unpredictable episodes of laughing and/or crying. AVP-923 consists of a combination of the NMDA antagonist/sigma1 receptor agonist dextromethorphan hydrobromide (DM) and the cytochrome P450 2D6 (CYP2D6) enzyme inhibitor quinidine sulfate (Q). DM has been under investigation for several years as a neuroprotective agent in stroke, neurosurgery and amyotrophic lateral sclerosis (ALS); however, it is rapidly metabolized by CYP2D6, reducing the drug's bioavailability at neuronal targets. The inclusion of Q inhibits the rapid first-pass metabolism of DM to increase systemic concentrations of the drug in the plasma and, in theory, increase the potential efficacy. The initial clinical data for AVP-923 in the treatment of PBA demonstrated the combination was effective, but exhibited significant side effects. Of particular concern to the FDA were increased QTc intervals reported in patients dosed with a 30-/30-mg dose of DM/Q. A subsequent phase III clinical trial assessing a lower dose of AVP-923 (20 or 30 mg DM/10 mg Q) for the treatment of PBA in patients with ALS or multiple sclerosis was implemented by AVANIR and demonstrated a favorable safety profile of AVP-923 while maintaining efficacy. Pending approval of the data from the FDA, AVP-923 would be the first FDA-approved treatment for PBA.

Topics: Animals; Clinical Trials as Topic; Dextromethorphan; Diabetic Neuropathies; Drug Combinations; Humans; Mood Disorders; Quinidine

Reports of rapid-onset but short-duration antidepressant effects in patients with treatment-resistant mood disorders after intravenous administration of ketamine have prompted efforts to find an agent with ketamine's properties that can be administered orally in repeated doses in order to sustain that action. One candidate for this dextromethorphan, and here the pharmacologic mechanism of action is compared and contrasted with that of ketamine.

Topics: Dextromethorphan; Drug Combinations; Excitatory Amino Acid Antagonists; Humans; Ketamine; Mood Disorders; Quinidine